From b54df61c7428ff50b21a03a53e3d580c6e84d1bf Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Wed, 12 Nov 2025 19:03:08 +0100 Subject: [PATCH] cpuidle: governors: teo: Decay metrics below DECAY_SHIFT threshold If a given governor metric falls below a certain value (8 for DECAY_SHIFT equal to 3), it will not decay any more due to the simplistic decay implementation. This may in some cases lead to subtle inconsistencies in the governor behavior, so change the decay implementation to take it into account and set the metric at hand to 0 in that case. Suggested-by: Christian Loehle Signed-off-by: Rafael J. Wysocki Reviewed-by: Christian Loehle Tested-by: Christian Loehle Link: https://patch.msgid.link/2819353.mvXUDI8C0e@rafael.j.wysocki --- drivers/cpuidle/governors/teo.c | 26 +++++++++++++++++++------- 1 file changed, 19 insertions(+), 7 deletions(-) diff --git a/drivers/cpuidle/governors/teo.c b/drivers/cpuidle/governors/teo.c index 88ed47e868b9c..8b80d73e518ed 100644 --- a/drivers/cpuidle/governors/teo.c +++ b/drivers/cpuidle/governors/teo.c @@ -148,6 +148,16 @@ struct teo_cpu { static DEFINE_PER_CPU(struct teo_cpu, teo_cpus); +static void teo_decay(unsigned int *metric) +{ + unsigned int delta = *metric >> DECAY_SHIFT; + + if (delta) + *metric -= delta; + else + *metric = 0; +} + /** * teo_update - Update CPU metrics after wakeup. * @drv: cpuidle driver containing state data. @@ -158,8 +168,9 @@ static void teo_update(struct cpuidle_driver *drv, struct cpuidle_device *dev) struct teo_cpu *cpu_data = this_cpu_ptr(&teo_cpus); int i, idx_timer = 0, idx_duration = 0; s64 target_residency_ns, measured_ns; + unsigned int total = 0; - cpu_data->short_idles -= cpu_data->short_idles >> DECAY_SHIFT; + teo_decay(&cpu_data->short_idles); if (cpu_data->artificial_wakeup) { /* @@ -195,8 +206,10 @@ static void teo_update(struct cpuidle_driver *drv, struct cpuidle_device *dev) for (i = 0; i < drv->state_count; i++) { struct teo_bin *bin = &cpu_data->state_bins[i]; - bin->hits -= bin->hits >> DECAY_SHIFT; - bin->intercepts -= bin->intercepts >> DECAY_SHIFT; + teo_decay(&bin->hits); + total += bin->hits; + teo_decay(&bin->intercepts); + total += bin->intercepts; target_residency_ns = drv->states[i].target_residency_ns; @@ -207,7 +220,9 @@ static void teo_update(struct cpuidle_driver *drv, struct cpuidle_device *dev) } } - cpu_data->tick_intercepts -= cpu_data->tick_intercepts >> DECAY_SHIFT; + cpu_data->total = total + PULSE; + + teo_decay(&cpu_data->tick_intercepts); /* * If the measured idle duration falls into the same bin as the sleep * length, this is a "hit", so update the "hits" metric for that bin. @@ -221,9 +236,6 @@ static void teo_update(struct cpuidle_driver *drv, struct cpuidle_device *dev) if (TICK_NSEC <= measured_ns) cpu_data->tick_intercepts += PULSE; } - - cpu_data->total -= cpu_data->total >> DECAY_SHIFT; - cpu_data->total += PULSE; } static bool teo_state_ok(int i, struct cpuidle_driver *drv) -- 2.47.3